In the prior art, U.S. Pat. No. 5,987,179, entitled “Method and apparatus for encoding high-fidelity still images in MPEG bitstreams” and issued Nov. 16, 1999 in the names of J. K. Riek et al., describes the coding of still pictures in an MPEG sequence. Furthermore, U.S. Pat. No. 5,959,690, entitled “Method and apparatus for transitions and other special effects in digital motion video” and issued Sep. 28, 1999 in the names of J. A. Toebes VIII et al., and U.S. Pat. No. 5,559,562, entitled “MPEG editor method and apparatus” and issued Sep. 24, 1996 in the name of W. Ferster, describe the insertion of transitions into MPEG bitstreams.
The patent by Riek et al describes different ways of encoding a still image in a bitstream when the decoding buffer is of a limited size. This is often the case in constrained parameter bitstreams such as those used by Video CD (VCD). The patent by Ferster describes a method for decoding two bitstreams, creating the transition effect, and then re-encoding the sequence. The patent by Toebes et al. describes a method for inserting transitions at the decoder.
The prior art has several limitations. The method described by Riek et al. does not teach how to insert transitions, nor is the method well suited for inserting transitions. The patent by Ferster involves a decoding and re-encoding, which is time consuming and will provide lower image quality. The patent by Toebes et al. describes the insertion of transitions, but it is performed at the decoder rather than at the encoder. That is, the frames are never inserted into the transmitted bitstream. This requires additional hardware at the decoder, which is an additional expense and is not standard-compliant.
What is needed is a method for efficiently inserting transitions into the bitstream with no loss of quality and no decoding required.